The SET Index is a Thai composite stock market index calculated by the prices of all common stocks (including unit trusts of property funds) on the main board of the Stock Exchange of Thailand (SET), except for stocks that have been suspended for more than one year. It is a market capitalization-weighted price index which compares the current market value of all listed common shares with its value on the base date of April 30, 1975, when the Index was established and set at 100 points.

The formula of calculation is as follows:

SET Index = ( Current Market Value x 100 ) / Base Market Value

The SET Index calculation is adjusted in line with modifications in the values of stocks resulting from changes in the number of stocks due to various events, e.g., public offerings, exercised warrants, or conversions of preferred to common shares, in order to eliminate all effects other than price movements from the index.

Besides the SET Index, which is calculated from the stock prices of all common stocks listed on The SET, The SET also provides other indices to investors that include the:

The following table shows the annual development of the SET Index since 1975.